What the numbers on a Pennsylvania cannabis label mean

By StashLog · 2026-09-28

THCa versus total THC, the mg/g trap, lot numbers and the QR code, and what is specific to Pennsylvania's medical-only program, explained line by line.

A Pennsylvania dispensary label packs a lot onto a small sticker: two or three cannabinoid numbers, sometimes a terpene list, a lot number, dates, warnings and a code. This guide reads a typical label line by line. It is written for patients who already hold a medical marijuana ID card and want to understand what they are looking at, not as legal advice. Where the rules matter, check the Pennsylvania Department of Health's current guidance, because regulations change.

First, the program you are buying in

At the time of writing, Pennsylvania's program is medical only. It was created by the Medical Marijuana Act of 2016 and is run by the Department of Health. To buy, a patient needs a certification from a practitioner registered with the program and a state ID card, and can only buy at a licensed dispensary.

That shapes the label in a few ways:

• Products are made by licensed grower/processors and sold by separately licensed dispensaries. The label names the grower/processor.
• The permitted forms are set by law. Pennsylvania allows dry leaf for vaporization, vape oils and concentrates, tinctures, pills and capsules, topicals and a limited range of other forms. The Act does not permit smoking. That is the law as written, and the label warnings say so.
• The Department of Health's regulations set what the label has to carry: product identity, the grower/processor, cannabinoid content, a batch or lot identifier, dates and required warnings, among other things. Brands add to that minimum, which is why two labels from the same dispensary can look quite different.

THCa and THC: two numbers for one thing

On a flower label you will usually see a large THCa number and a much smaller THC number. They are not two different ingredients in the way the label layout suggests. THCa is the form the plant makes, and heat converts most of it into THC. On raw flower almost all of it is still THCa.

That is why many Pennsylvania labels also print Total THC, which combines the two with a standard formula:

Total THC = THC + (THCa × 0.877)

The 0.877 reflects the difference in molecular weight between THCa and THC: when THCa converts, it loses a small piece of itself as carbon dioxide, so every gram of THCa can become at most 0.877 g of THC. A flower label reading THCa 25% and THC 0.8% works out to a Total THC of about 22.7%.

If a label gives only THCa and THC with no total, you can do the arithmetic yourself. If it gives only a total, that is the number to compare between products.

The same logic applies to CBD and CBDa, and some labels print a Total CBD worked out the same way.

The mg/g trap

Labels switch between percent and milligrams per gram, sometimes on the same sticker. They are the same ratio: 10 mg/g is 1%. So:

• 250 mg/g THCa is 25% THCa.
• 850 mg/g THC in a vape oil is 85%.

The trap is reading mg/g as the amount in the package. It is the amount per gram. A half-gram cartridge at 850 mg/g carries about 425 mg of THC in total, not 850. A 3.5 g package of flower at 250 mg/g THCa carries about 875 mg of THCa.

Some products, especially tinctures and capsules, give milligrams per dose or per millilitre instead. Read the unit next to every number before comparing two products, and compare like with like.

Terpenes on the label

Many Pennsylvania brands print their product's top terpenes, and some print a total terpene figure. When they do, the numbers come from the batch's lab testing, the same as the cannabinoids.

Two cautions. A top-three list is a small slice of the full panel, so two products can share a top three and still differ below it. And the total only counts the terpenes the lab looked for, so totals are most comparable between products tested by the same lab. The guide on reading a lab sheet covers this in more detail.

Lot numbers, batch numbers and the QR code

Every package carries an identifier that ties it to the batch it was made in and the lab results for that batch. Labels call it a lot number, a batch number, a package ID or several of these at once.

The lot number is the single most useful thing on the label to write down. It is the only line that separates this package from every other package sold under the same product name. When you log a jar in StashLog, the lot goes with it, and the lot ledger lines up every lot of the same product you have had.

The QR code is where expectations often go wrong. On many Pennsylvania packages the code carries a package or tracking identifier from the state's seed-to-sale system rather than a link to a public lab report. Scanning it may give you a string of characters, not a Certificate of Analysis. Some brands do link a QR to their own results page; many do not. Do not assume a code opens the sheet.

If you want the full lab report, ask the dispensary: they receive the certificate for every batch they sell. Many dispensaries' online menus also carry the lab figures for each listed product.

Dates

Look for some combination of:

• Harvest date: when the plants were cut.
• Package date: when the product was sealed.
• Test date: when the batch was tested, sometimes on the label and always on the lab report.
• An expiration or best-by date, where the product carries one.

The label's cannabinoid and terpene figures describe the batch when it was tested. Flower keeps changing after that: terpenes slowly evaporate, and THC slowly breaks down into CBN. A long gap between harvest and the day you buy is worth noticing. It does not make a jar bad, but it does mean the label is describing an earlier version of it.

Warnings and the small print

Pennsylvania labels also carry required warnings, the grower/processor's name and licence details, and handling instructions. These are set by regulation and read much the same from brand to brand. They are worth reading once; after that, the lines that change from package to package are the ones above.

Putting it together

When two jars sit side by side at the counter, the quickest honest comparison is:

1. Same units on both? Convert mg/g to percent if needed.
2. Total THC, if you care about content, calculated the same way on both.
3. The terpene list, compared with jars you have already rated.
4. The dates, for how long each has been sitting.
5. The lot number, written down, so next time you know which batch you are talking about.

StashLog reads that last line for you: photograph the label and it pulls the lot, the cannabinoids and whatever terpenes are printed, so the next comparison starts from your own record instead of your memory.